Automatic gas ignition and burner control system



July 23, 1957 H. E. MORRISON 2,800,176

AUTOMATIC GAS IGNITION AND BURNER CONTROL SYSTEM Filed Sgpt. 27, 1954 2 Shee ts-Sheet 1 49 Y 17 w r I 11 Van far" 15 490 0 E/Vaeexsom July 23, 1957 H. E. MORRISON AUTOMATIC GAS IGNITION AND BURNER cbNTRoL SYSTEM Filed Sept. 27, 1954 I 2 She etS-Sheet 2 .571 2 17 far 15514 040 E Maze/ 0 4 Am, w; kw,

States Patent Ofiice 2,800,176 Patented July 23, 1957 AUTOMATIC GAS IGNITION AND BURNER CONTROL SYSTEM Harold E. Morrison, Benton Harbor, Mich., assignor, by mesne assignments, to Whirlpool-Seeger Corporation, St. Joseph, Mich, a corporation of Delaware Application September 27, 1954, Serial No. 458,455

7 Claims. (Cl. 158-125) This invention relates to automatic pilots and more particularly to electrically operated automatic pilots for gas burners, to turn the gas supply on and ofi upon failure in the gas and electric system, and to ignite the main burner.

Heretofore, electrically ignited pilots and automatic controls for the gas supply system for igniting the main burner and turning off the gas supply upon failure of the gas supply or electric controls have been used in various types of gas heated apparatus. Such pilots, however, have been slow to operate, both in turning on and turning off the gas supply and in igniting the main burner, with the result that there is frequently an accumulation of gas, due to the time lag in shutting off the gas after the failure, or to the time lag in igniting the burner after the gas supply is turned on, with the result that minor explosions frequently occur. Due to this difliculty in providing a positive and fast acting automatic pilot the standards which have been set up by the American Gas Association of Cleveland, Ohio, allow a time variation of up to five minutes to turn off the main burner after a current interruption. While this time lag is exceedingly long, it is not exceedingly dangerous for certain types of apparatus, such as ovens and heating furnaces, even though undesirable and a potential source of danger and has of necessity been set up as a standard because no pilot has heretofore been found which would immediately shut-01f the gas supply as soon as the pilot flame goes out or a current interruption occurs.

My invention has as its principal objects to provide an automatic pilot which will instantaneously close the gas supply and prevent unburned gas from passing through the main burner, upon interruption of the electric system or upon failure or excessive pressure in the gas supply line.

Another object of my invention is to provide an automatic pilot and an electric igniter for the pilot flame wherein the gas supply will be immediately shut-off upon interruption of the electric system, and wherein the power may be turned back on again as soon as the pilot flame is out.

A further object of my invention is to provide an automatic pilot and electric igniter for the pilot gas which will automatically shut-01f the gas supply if the gas pressure is too high or too low.

A still further object of my invention is to provide a simplified and novel form of control for an automatic pilot so arranged as to render it impossible to supply gas to the main burner when the pilot is out.

A still further object of the invention is to provide an automatic gas ignition and burner control system in which the ignition system and master and main burner valves are shut-off except when the gas pressure issuch as to assure safe ignition of the pilot and main burners.

This application is a continuation-in-part of my applications, Serial No. 168,638, filed June 16, 1950, now abandoned, and entitled Automatic Gas Ignition and Burner Control System, and Serial No. 335,646, filed 2 February 9, 1953, and entitled Electrically Controlled Safety Igniter Circuit for Gas Burners.

These and other objects of my invention will appear from to time as the following specification proceeds and with reference to the accompanying drawings wherein:

Figure 1 diagrammatically shows an automatic gas ignition and burner control system constructed in accordance with my invention and connected in the burner and electric circuit of an automatic clothes dryer; and

Figure 2 illustrates a modified form of gas ignition and burner control system having my invention embodied therein.

The automatic pilot of my invention is herein shown as being operative to ignite and control operation of the burner of a clothes drier, and as being connected in the electric control circuit for rotatably driving the drier although it need not be connected in such a circuit and may be utilized in any desired gas burner circuit. The control circuit for the drier is somewhat similar to that shown and disclosed in my joint application with Peter E. Geldhof et al., Serial No. 208,708, filed on January 31, 1951, and now Patent No. 2,678,814 dated May 18, 1954, so the drier and the circuit thereto need only be described herein to the extent suflicient to make my present invention readily understandable.

A pipe 10, connected to a gas supply line is shown as delivering gas to a pilot or main gas supply valve 11 operated by a solenoid 12. A pipe 13 connects the main gas supply valve 11 with a control valve 15 for a main burner 16. A pilot burner 17 leads from the supply side of the valve 15 to a position adjacent the burner 16 for igniting said burner and is supplied with gas as long as the valve 11 is open. The pilot flame is ignited by a glow coil 19 energized by the secondary of a transformer 26. The glow coil 19 is positioned adjacent the pilot 17, but for convenience in illustrating the control circuit, said glow coil is herein shown as being remote from the pilot. A solenoid 21 is provided to operate the main burner valve 15.

The valves 11 and 15 may be of any well known form of solenoid-operated gas control valve, one form of construction of said valves being illustrated in my joint patent with Peter E. Geldhof et al., No. 2,678,814 referred to before. Said valves are no part of my present invention so need not herein be shown or described further.

Electric power to drive the drier motors and energize the system is provided through conductors 23 and 24, connected with a suitable source of electric power. A switch 25 is shown as being connected in the conductor 23, to deenergize the entire drier circuit. A motor 26 is shown as being provided to drive the drier drum and a timing motor 27 is provided to drive the timer for timing the operations of the drier, and to control the energization of the solenoid 21, to turn the supply of gas for the drier burner 16 on and off at predetermined time intervals, as is well known to those skilled in the art and no part of my present invention so not herein shown or described further. A switch 29 is shown as being provided in the conductor 24. This switch may be a door operated switch and is shown as connecting a lamp 311 in the circuit upon opening of the door, to light the inside of the drier, and as disconnecting the motors 26 and 27, and solenoid 21 from the circuit when the door is opened.

It should here be noted that upon door opening movement the gas supply to the burner 16 is turned off, but the gas supply valve 11 remains open and pilot burner 17 remains on to again ignite the burner when the door is closed, provided the switch 25 remains closed.

Switches 31 and 32 operated by the timer motor 27 are likewise shown as beingconnected in the control system. The switches 31 and 32 are shown as being connected in series in the return from the solenoid 21 to the switch 2 9,..through conductors 33, 3 4 and 35. The conductor 33 a a a usta l ermqsta .36 therei whi may be manually set to control the drier temperature. It also has a safety thermostat 37 therein. The safety thermo stat 37 i s. shownas being inv the.,form .ofabirnetalswitch and opens the circuit to the coil 21, if .for any reason the temperature within the drier should become too high and the thermostat 36 should not .function.

The return'from themotors 26 and 27 .is connected in the cond l c ti jr 34betjween the switches31 and 32. The

switches 31 and 32 are closed upon the setting of' the timer motor 27t0 a timed position and will remain closed for predetermined periods of time. The switch 32 may open at a delayed time interval after opening oftheswitch 31 tocirculate the clothes after the mainburneris turned 011.

A ,primarycoil 3.8 of the transformer .20, energizing the glow coil 19 through the secondary of said transformer, is c onnecte d in the'circuitthrough a contact 45 and switch arm .49 of a time detecting pilot switch 46, when said flame detecting switch is .in its'cold position. The contact-451s hereinafter referred to as the cold'contact of said switch. The connection from said contact '45 to'lenergize the primary .38 of thetransforfner includes a conductor 39 connected withthe contact 45, the contactsyof a bi-metal warp switch 40 and a conductor 42 connected with the line 24. A heater coil 41 of the bimetal warp switch 40 is'likewise connected with contact 45 through the conductor 39 and a conductor 43.

The heater coil 4,1'is provided to heat the bi-metal warp switch 40 and open the contacts thereof in a predetermined time delay interval and deenergize the ignition circuit, should the pilot burner fail to ignite in a period of time of from approximately three to five minutes at normal line voltage. The contacts of said warp switch 40 are normally closed, and open to deenergize the solenoid 12 of the pilot or main gas supply valve 11, and shut-off the supply of gas in case the flame detecting switch 46 should not passfrom its cold to the hot position, as when the pilot should fail to ignite.

Upon opening of the warp switch 4! and failure of the switch 46 to pass from its cold to hot position, the circuit to the primary coil 38 of the transformer 20 will be opened, deenergizing transformer 20 and glow coil 19. The heater coil 41, however," will remain energized through the contact arm 49 and contact 45 of the flame detectorswitch 46.

The solenoid 12 is connected in the circuit through a conductor 44 connected with the conductor 23,'a' conductor 47 connected from the conductor 44 to said solenoid and a conductor 48 connected from said solenoid through the contacts of the'warp switch 40 and'through the contacts of said warp switch to the conduc'tor' 42. The contacts of the warp switch 40 are initially closed when starting operation of the drier 'and remain closed during normal operating conditions to energize the solenoid 12 of the main gas supply valve 11.

The circuit to the heater coil 41 is closed as long as the switch is closed and the contact arm 49 of the flame detecting switch 46 is in engagement with the cold contact 45. The heater coil 41 will therefore warm the switch 41 until the pilot is ignited and the flame detector switch 46 passes from its cold to its hot position. Once the warp switch 40 opens, said switch will remain open until the heater coil has cooled upon the breaking of the circuit thereto as by opening of the switch 25.

The flame detecting pilot switch 46 may be of a type similar to that shown and disclosed in my joint Patent No. 2,678,814 with P. E. Geldhof et al., mentioned before, and i no part of "my present invention so need not herein be shown or described in detail. Upon the lighting of the pilot 17 by the glow coil 19, the heat of the pilot flame will move a contact member 49 of theswitch into positionto close a circuit through the contact 50 of said switch, which willhereinafter be termed the hot ,qqnta .Q sai switch- In normal operation after the flame detecting switch 50 has moved to its hot position, to efiect energization of the solenoid 21 of the main burner valve 15, the main gas supply valve solenoid 12 remains energized through the contacts of the warp' switch 40. The primary 30 of the transformer 20 and the heater coil 41 are deenergized because of the shifting of thecont act arm 49 to its hot position.

The hot contact 50 is connected with a conductor 51 shown as being connected with a contact arm 52 of a relay 53. Said contact arm 'is'engageable with a contact 54 of said relay when said relay is energized, to close the circuit to the solenoid 2 1 and open the main gas burner under control of said relay and said hot contact 50 of the switch 46.

An operating coil 55 of the relay 53 is herein shown asbeingconnectedin series with a coil 56 of a relay 57. The relay 5.7 is adapted'ito close a'ci'rcuit from the cold contact 45 of the pilot switch46 througha cohtac't59 and energizethe c'oils 56 and 55andclos'e said relays; When the relay 57 has been closed by the energization of'its coil. throughthe contact 59, the cir'cuit'thr'ough saidcpr'rtact is .b'rolgemand 'the'coils 5.6 and 55 areheld energized'through a 'contact60ofthe relay 57.' Current is conducted'to the contact 60 by'a conductor 70' directly connected with'ftheconductor :44. While I herein show tworelays one of which serves to energize and hold the relays closed'andthe "other of which serves to complete a circuit through the solenoid coil 21 to close the main burner'valve v15,'it should he understood that I need not have .two relays, and that one relay with multiple F sets of contacts will serve as well, and that two'relays are only shown as'a matter of convenience in illustrating the circuit. Y

A'conductor 61 having two pressure operated switches 63 .and 64 thereinj-herein shown as being diaphragm switches of a suitable construction serves to connect the coils 55 and 5.610 the return 24. T The diaphragm chamber of the switch 164 is connected with the gas supply line 13 through a pipe 65 connected to one side of the diaphragm (not shown) of the diaphragm switch 64 as indicated at 66. A branch pipe 67 leading from'the pipe .65is connected to the opposite side of the diaphragm chamber and diaphragm of the switch '63 from the switch 64. The switches 63 and 64 areh'e'ld in a closed posi tion during normal gas pressure in the line 13. The switch .63, (however, opens its'co'ntacts upon a reduction in gas pressure in said supply line below a predetermined safe value while the switch 64 opens its contacts upon pressure in saidgas supply-line above a predetermined safe value. The circuit to the coils for the relays 53 and 57 will thus be broken and said relays 'will open upon a reduction or increase in 'pre's sure inthe gas line 13'below or above a predetermined normal "or safe value' The opening of said relays will thus deenergize the solenoid 21' and effect closing the burner valve 15. The pilot valve 11, however, will remain open to again ignite the main burner 16 when the pressures in the line"1-3"again reach the desired safe operating value. If, howeve'nth'e pressure should be so low that the pilot flame will go out, the contact arm 49 of the flame detector switch 46 will move to .the cold position. The mainburner 'valve 15 then cannot be opened until the pilot has been" ignited and the circuit through the hot contact 50 of said switch 46 is closed.

Upon failure of power, the relays 57 and 53 will immediately open, deenerg'izing' the coil of the solenoid 21 and effecting closing of the main burner valve 15. The solenoid 12-of the pilot valve 11 will'also be deenergized, effecting closing'ofsaid valve. The contact'arm 49 of'the flame detecting switch 46 will then move to engage the contact 45 and the circuit will befin the open'position shown, assuming thedrier door is closed. When power heater coil 41. This will energize the glow coil 19 to ignite the pilot l7 and will also heat the bi-metal Warp switch 4%), preparatory to opening said switch after a predetermined time interval if the pilot burner 17 should fail to ignite.

The coils 55 and 56 of the relays 53 and 57 will also be energized throughconductor '44, contact arm 49, contact 45, conductors 39, 43 and 69, contact 59, conductor 61, pressure switches 63 and 64 and conductor 24. This will break the circuit through the contact 59 and make the circuit through the contact 60 of the relay 57, to hold said relays closed. It will also close a circuit through the contact 54 of the relay 53 and connect the solenoid coil 21 of the main burner valve 15 to the contact 50 of the flame detecting switch 46.

As soon as the pilot 17 is ignited, the heat of the pilot flame will move the contact arm 49 of the flame detecting switch 46 into engagement with the contact 50 and complete a circuit through the coil of the solenoid 21 through the conductor 51, contact 54 of relay 53, and to the return through the thermostats 36, 37, the conductor 33 and switches 31, 32 and 29. This will effect opening of the main burner valve.

If, however, the glow coil 19 for any reason should fail to ignite the pilot burner 17, the arm 49 will stay in engagement with the contact 45. The heater coil 41 being energized through the cold contact 45 will eltect opening of the bi-metal warp switch 40 in a delayed time interval. This will deenergize the solenoid 12 and efiect closing the pilot or main gas supply valve 11. The primary 38 of the transformer 29 and the glow coil 19 will also be deenergized. The circuit to the coil of the solenoid 12 of the main gas supply valve 11 can, therefore, never be completed until the heater coil 41 has cooled by opening 0 fthe switch 25, and the warp switch 40 has closed its contacts. The switch 25 may then be closed and the pilot burner may be ignited. The main burner valve 15 may then be opened when the pilot has generated suflicient heat to move the contact arm 49 into engagement with the hot contact 50.

Also, the circuit to energize the coils 55 and 56 to complete the circuit through the contact 50 of the pilot switch 46 to the contact 54 of the solenoid 53 can only be completed when the pressure in the line 13 is a predetermined normal safe pressure, the switch 63 opening when the pressure is below a safe normal pressure, and the switch 64 opening when the pressure is above a safe normal pressure, thus protecting the burner against excessive pressures, or against pressures so low that the flames in the burner and pilot are likely to go out.

Also, if at any time during operation of the drier, the pressure should vary below or above predetermined safe normal pressures the relays 53 and 57 will both open. The burner valve 15 will then close, the pilot valve 11 remaining open until a power interruption. .When this occurs, the relay 53 and 51 can only be closed to again open the burner valve 15, by opening the switch 25, to break the circuit through the coil of the solenoid 12, and allowing the pilot flame to go out, and accommodating the pilot switch to cool and open the circuit through the contact arm 4% and contact 50, and close the circuit through the contact arm 49 and contact 45.

The relays 53 and 57 can, therefore, only be reclosed, if for any reason the circuit through their coils has been interrupted, through the cold contact 45 of the flame detecting switch 46. Also the main burner valve 15 can only be closed after the pilot has been ignited and has generated sufilcient heat toopen the-circuit through the contact arm 49 and contact 45 and, move the contact arin 49 to close a circuit through the contact 50 of said flame detecting pilot switch, thus assuring the absence of raw gas within the drier cabinet.

. In the modified form of control circuit illustrated in Figure 2, the elements like those in Figure 1 will be referred to by like reference numerals plus an aflix a.

In this modified circuit, a relay 69 is shown as taking the place of the two relays 53 and 57 and as having a solenoid coil 71 energized through the contact 59a, a contact bar 72. of said relay and a contact 73, when the flame detecting switch 46a is in its cold position, with the contact arm 49a in engagement with the contact 45a.

The solenoid coil 71 is energized through the conductor 70a, contact 60a, the contact bar 72 and a, contact 74 when the flame detector switch 46a has passed to its hot position to engage the contact on 49a with the contact 50a by the heat of the pilot flame. The solenoid coil 71 is shown as being connected to the conductor 24a through a conductor 75.

The relay 69 also has a second contact bar 76 movable with the contact bar 72 and completing a circuit from the hot contact 50a of the flame detector switch 46a, the conductor 51a, a contact 77 through the contact bar 76 to the contact 54a to energize the solenoid coil 21a of the main burner valve 15a when the pilot burner has been ignited and has generated suificient heat to effect movement of the contact arm 49a into engagement with the hot contact 50a.

The circuit to energize the solenoid 21a is thus the same as the circuit in the form of my invention illustrated in Figure 1 except that a single relay 69 has been substituted for the two relays 53 and 57.

Two pressure operated switches 80 and 81 are shown as being provided in the conductor 42a to prevent the energization of the solenoid coil 12a and the opening of the main gas supply valve 1111 except when the gas pressure on the supply side of said main gas supply valve is a predetermined normal pressure.

The pressure switches 80 and 81 are diagrammatically shown as being diaphragm switches like the switches 63 and 64 illustrated in Fig. 1 and include diaphragm chambers 82 and 83 respectively connected in the supply pipe 10a on the supply side of the main gas supply valve 11a through a pipe 84. The diaphragm chamber 83 is connected with the pipe 84 to one side of the diaphragm (not shown) of the diaphragm switch 81 at 85. A branch pipe 86 leading from the pipe 84 is connected to the opposite side of the diaphragm chamber 82 from the connection of the pipe 84 to the diaphragm chamber 83.

The switches 80 and 81 are closed upon normal. gas pressure in the pipe 10a. The switch 80, however, opens its contacts upon a reduction in gas pressure in the gas supply line 10a below a predetermined safe value while the switch 81 opens its contacts upon the increase in pressure in said gas supply line above a predetermined safe value.

The pressure switches 80 and 81 thus assure that the gas pressure is up to normal before the main gas supply valve can be opened and the glow coil 19a can be energized to ignite the pilot burner 17a. This prevents the collection of unburned gas in cases where the pressure may be so low that the pilot will not ignite until there has been an undue accumulation of gas in the drier cabinet, and also prevents failure of the pilot to ignite by excessive gas pressures high enough to keep the pilot from igniting until there has been a dangerous accumulation of gas in the drier cabinet. The pilot burner 17a is thus only supplied with gas when the gas pressure is such that the glow coil 19a will readily ignite the pilot.

It has been found in practice that one of hazards in operating a gas burner system, particularly by unskilled persons, lies in the inadvertent pulling out of the electric supply cord .or opening one of the main electrical control'iswit'ches and then. immediately reestablishing the ele ricpower supply to the system.

It is highly desirabletoprovide safety means in a gas bnrner control system which will, under ,such circumstances, shut offiboth the mastervalve ,11 1 as well asthe main bur 'ner valve a and prevent their reopening until the flame detector switch has atleastreturned to its cold where igniter is again energized.

.In'the form of .my invention 'shownin Figure 1 ofthe drawing, .the main burner valve cannot be reopened under such circumstances until the flame detector switch is recycledthrough itscold position, but means is not providdinthis flrst form of my invention for preventing reopening of thelmaster valve.

ln the form of my invention illustrated in Figure 2, eans'ts also provided for preventing reopening of the This is accomplished by initially effecting energ zationtof the master valve through the cold contact of the flame detector switch and then providing a holding circuit therefor which lay-passes the flamedetector switch. H

Specifically, the upperend of the coil 12a is connected totheimovablelswitch ,element87 which is actuated by thearrnature ds of the solenoid 12a. This switch also includes a stationary contact 89 and a stationary contact 901 The movable switch arm 87 normally connects contact 89 when the solenoid 12a is deenergized and while the stationary contact 90 is connected to the switch arm 87 when the solenoid 12a is energized. The contact 89 is directly connected to the cold position contact 45a of the flame detector switch 46a while the stationary contact '90 is directly connected to conductor 4445.

From the above description, it will readily be appreciated that the master valve 114: is opened by initial energization of the circuit which includes the pressure switches 80 and .81, the warp switch 40a, the solenoid 12d ofthe valve 11a, and the flame detector switch 46a. Upon a flow of electric energy through the solenoid 1211, the master valve 11g is opened and the movable switch arm 87 moves to its upper position in engagement with contact 90 to establish a holding circuit around the flame detectingswitch. Even upona momentary interruption of tlie pow er circuit, the solenoid 1211 becomes deenergized, the holding circuit opens, and the switch 87 drops back toits lower position. The master valve 11a can now only bereopened by reenergization of the solenoid 125 through the flame detector switch.

The same result will occur if there is even a momentary variation in gas pressure in the gas supply main 10a outside of the predetermined range, for this will cause either pressure switch St) or pressure switch 81 to open and effect deenergization of the solenoid 12a. It will thus be seen that a high degree of safety is provided for any abnormal operation, irrespective of whether it is a power failure or an abnormal fluctuation in gas pressure.

It .will be understood that various modifications and variations of the present invention may be eflectedwithout departing from the spirit and scope of the novel concepts thereof. '7

I claim as my invention:

1. In an automatic gas igniter and burner control system, a gas supply line,a main burner connected thereto, a pilot 'burner also connected thereto for igniting said main burner, electrically energizable'means for igniting said pilot burner, a valve in said gas supply line on the supplyIside of said pilot and said main burner, a solenoid for operating said valve, a main burner valve on the supply side of said main burner, a solenoid for operating said main burner' valve and a safety thermostatic switch in series with the coil for said last mentioned solenoid, a flame detecting pilot switch closing a circuit through one contact'whencold and through another contact when heated by the presenceof the pilot flame, a relay having a coil'and a plurality of contacts, an energizing circuit to sai lielaycoil through oneof said contacts and the cold eontacts of said flame detectingswitch, a :secondenergizingcircuit to said relay coil through another of said contacts, said second .energizing circuitclosing whenlsaid relay coil is energized, an energizing circuit for said solenoid for said main burner valve through a ,third .set of contacts and including the hot contacts'of said flame detecting switch, and means operative upon energization of said relay coil for closing said third set of contacts.

2. In an automatic gas igniter and burner control system, a gas supply line, a main burner connected thereto, a pilot burner also connected thereto for igniting :said main burner, electrically energizable means igniting said pilot burner, 21 valve in said gas supply line on the supply side of said main and pilot :burners, a solenoid for operating said valve, a burner valve on the supply side of said main burner, a solenoid for operating said burner valve, a flame detecting pilot switch closing a circuit through one contact when cold and through another contactwhenheated by the presence of a pilot flame, a relay having a coil and a plurality of contacts operated thereby, one of said contacts being closed when said relay coil is deene'rgized and connecting the cold contact of said flame detecting switch with said relay coil, to energize said relay coil and open said one contact, another of said contacts being opened when said relay coilis deenergized and closing upon energization of said relay coil, to maintain the energizing circuit to said relay coil and hold said contacts closed upon movement of said flame detecting switch from a cold to a hot position, an energi zing circuit from the hot contact of said flame detecting switch through a third set of contacts of said relay, and means operative upon energization of said relay coil for closing said thirdset of contacts to energize said main burner solenoid upon movement of said pilot switch to a hot position only, said relay coil being initially ener-v gizable only through the cold contacts of said flame detecting switch, and fluid pressure operated switching means connected with said gas supply line and deenergizing said relay coil upon variation in pressure in said main gas supply line above or belowa predetermined normal pressure range.

3. In an automatic gas igniter and burner control system, a gas supply line, a main burner connected thereto, a pilot burner also connected thereto for igniting said main burner, a valve in said gas supply line on the supply side of said pilot and main burners, a solenoid for operating said valve, means for igniting said pilot, a main burner valve on the supply side of said main burner, a solenoid for operating said main burner valve and a safety thermostatic switch in series with the coil for said last mentioned solenoid, a flame detecting pilot switch having two contacts and closing the circuit through one contact when cold and through the other contact when heated by the flame of said pilot burner, a relay having a coil, a contact arm operable by said relay coil, two contacts either of which is engageable with said contact arm, one of said contacts being connected with the cold contact of said flame detecting switch and completing a circuit through said contact arm and relay coil when said relay coil is deenergized andthe other of said contacts being connected to hold said relay coil closed upon movement of said contact arm from said one contact to the other of said contacts, a conductor connecting the hot contact of said pilot switch with a third set of contacts, a connection from said third contacts to the coil of the solenoid for operating said main burner valve, and means operable upon the energization of said relay coil for closing said third set of contacts and energizing said solenoid operating said main burner valve upon movement of said flame detecting pilot switch from a cold to a hot position.

4. In an automatic fuel ignition and burner control systemincluding a pilot burner and a valve controlling the supply of fuel to said pilot burner, a main burner and a burner valve in series with said first valve for controlling the supply of fuel to said main burner, electromagnetic means for operating said first valve, electromagnetic means for operating said burner valve, a pair of electrical supply lines, a thermal switch responsive to heat of the pilot burner flame and having amovable contact connected to one of said supply lines, a cold contact normally engaged by said movable contact, and a hot contact engaged by said movable contact when said switch is heated to a predetermined temperature, an energizing circuit from said cold contact to the other of said electrical supply lines, a thermally operated time delay relay having electrically energizable operating means therefor in said last-mentioned circuit and having normally engaged stationary and movable contacts completing an energizing circuit to said electromagnetic means for operating said first valve, a relay having a coil, first and second fixed contacts and a movable contact normally engaged with said first contact and moved into engagement with said second contact by energization of said coil, means connecting said relay coil through said first contact of said relay to said cold contact, means connecting said second contact of said relay to one of said electrical supply lines; a third set of normally open contacts, means operative upon energization of said relay coil to close said third set of contacts and connect said electromagnetic means for operating said burner valve to the other of said electrical supply lines to energize said electromagnetic means to operate said burner valve to supply fuel to said main burner.

5. In an automatic gas burner ignition and control system, a gas supply line, a main gas burner connected to said gas supply line, a burner shut-oif valve on the supply side of said main gas burner, a solenoid for operating said valve, a pilot burner connected to said gas supply line on the supply side of said burner shut-01f valve, a main gas supply valve on the supply side of said pilot burner, a solenoid for opening said valve, a source of electric power comprising a plurality of conductors, an energizing circuit from said conductors to said solenoid for operating said main gas supply valve including a thermal operated time delay relay therein having a stationary contact and a movable switch arm normally engaging said contact and electrically energizable means for disengaging said switch arm from said contact, an energizing circuit from said conductors to said main burner shut-off valve having a thermally operated switch therein responsive to the heat of the pilot flame and having a cold and a hot contact, an energizing circuit from said cold contact to said electrically energizable means for operating said movable switch arm of said time delay relay, an energizing circuit from said hot contact to said solenoid for operating said burner shut-off valve, an initial energizing circuit including a relay coil and a holding circuit for the relay coil including a holding switch closed upon energization of the relay coil, whereby said relay coil is initially energized through said cold contact and is maintained energized through said hot contact, said first mentioned energizing circuit for said main gas supply valve having pressure operated switching means therein connected between one of said main line conductors and said time delay relay, and opening upon variations in pressure on the supply side of said main gas supply valve from a predetermined normal pressure.

6. In an automatic gas burner ignition and control system, a gas supply line, a main gas burner connected to said gas supply line, a burner shut-01f valve on the supply side of said main gas burner, a solenoid for operating said valve, a pilot burner connected to said gas supply line on the supply side of said burner shut-off valve, a main gas supply valve" on the supply side of said pilot burner, a solenoid for opening said valve, a source of electric power comprising a plurality of conductors, an energizing circuit from said conductors to said solenoid for operating said main gas supply valve including a ther- 10 mal operated time delay relay therein having a stationary contact and a movable switch arm normally engaging said contact, and electrically energizable means for disengaging said switch arm from said stationary contact, an energizing circuit from said conductors to said main burner shut-off valve having a thermally operated switch therein responsive to the heat of the pilot burner flame and having a cold and a hot contact, an energizing circuit from said cold contact to said electrically energizable means for operating said movable switch arm of said time delay relay, an energizing circuit from said hot contact to said solenoid for operating said burner shut-off valve, said' energizing circuit for said main gas supply valve having two pressure switches connected with the supply side of said main gas supply valve, one of said pressure switches being operable to open the circuit to said solenoid for said main gas supply valve upon increases in pressure over predetermined normal pressures, and the other of said pressure switches being operable to open the circuit to said solenoid for said main gas supply valve upon decreases in pressure below predetermined normal pressures, to prevent opening of said main gas supply valve except when the gas pressure on the supply side of said valve is at a predetermined normal pressure, and shutting off the supply of gas whenever the pressure on the supply side of said main gas supply valve varies from said predetermined normal pressure.

7. In an automatic gas burner ignition and control system, a gas supply line, a main gas burner connected to said gas supply line, a burner shut-ofl valve on the supply side of said main gas burner, a solenoid for operating said valve, a pilot burner connected to said gas supply line on the supply side of said burner shut-01f valve, a main gas supply valve on the supply side of said pilot burner, a solenoid for opening said valve, a source of electric power comprising a plurality of conductors, an energizing circuit from said conductors to said solenoid for operating said main gas supply valve including a thermal operated time delay relay therein having a stationary contact, a movable switch arm normally engaging said contact and electrically energizable means for effecting disengagement of said switch arm from said contact, an energizing circuit from said conductors to said main burner shut-oil valve having a thermally operated switch therein responsive to the heat of the pilot burner flame and having a cold and a hot contact, an energizing circuit from said cold contact to said electrically energizable means for efiecting operation of said movable switch arm of said time delay relay, an energizing circuit from said hot contact to said solenoid for operating said burner shut-off valve, said energizing circuit for said main gas supply valve having two pressure switches connected with the supply side of said main gas supply valve, one of said pressure switches being operable to open the circuit to said solenoid for said main gas supply valve upon increases in pressure over predetermined normal pressures, and the References Cited in the file of this patent UNITED STATES PATENTS 2,005,224 Dunham et al June 18, 1935 2,138,796 Sparrow Nov. 29, 1938 2,371,020 Beam Mar. 6, 1945 2,440,700 Rosche May 4, 1948 2,456,147 Ray Dec. 14, 1948 2,678,814 Geldhof et a1. May 18, 1954 

